>It means the key is around in plain text in the memory of ssh or ssh-agent. Which means it's extractable by an attacker. An exportable key does all the signing inside the secure enclave and never exposes the decrypted key to OS memory.

But malware can just tell the secure enclave to export the key? Yes, they'll have to write new code to do that, but it's not particularly hard (it's 1 line code from your example above), and it's security through obscurity.

The export operation is guarded by TouchID. So the malware needs to trick you into performing the TouchID gesture.

But yeh the malware only needs to trick you to hit TouchID once. Instead of on each sign operation. So if that's in your threat model don't make the key exportable.

The malware would have to prompt for biometric authentication before exporting.